The present invention relates to a photosensitive member, and more particularly, to an organic photosensitive member having a surface protective layer thereon.
Recently prevailing are organic photosensitive members composed of an organic photoconductive material dispersed in a binding resin, since they are more hygienically handled, and more suited for commercial production than those made of selenium, cadmium sulfide, or the like.
The organic photosensitive members are, however, low in hardness, and therefore, are easily abraded and flawed due to the friction with transfer paper, cleaning members, and a developer during their repeated workings.
To eliminate these problems, there is proposed a surface protective layer with a high hardness formed on the surface of an organic photosensitive member.
For example, amorphous hydrocarbon is a well known material for such a surface protective layer featured by high hardness as shown in Japanese Patent Unexamined Publication Nos. Sho 63-97962, Hei 1-4754, and Hei 1-86158 which disclose techniques of forming a surface protective layer of amorphous hydrocarbon on the surface of an organic photosensitive member.
Desirably, a surface protective layer is formed on organic photosensitive layer immediately after the formation of the organic photosensitive layer. But, as a matter of fact, organic photosensitive layers alone are first mass-produced at once, and then, amorphous hydrocarbon layers are formed thereon for simplification of manufacturing process, or due to a problem of machines such as difference in yield between an organic photosensitive layer forming apparatus and an amorphous hydrocarbon layer forming apparatus or the like. Generally, the period from the organic photosensitive layer forming step to the amorphous hydrocarbon layer forming step is several days to one month or so, during which the organic photosenstive layers are stored (this stored time is referred to as "stock time is process").
During this period, the organic photosensitive layers are oxidized at their surfaces with the passage of time by the oxygen in the atmosphere. It is to be noted that when an amorphous hydrocarbon layer is formed on an organic photosensitive layer having such an oxidized layer thereon, the amorphous hydrocarbon layer peels because of poor adhesivity of the amorphous hydrocarbon layer to the oxidized layer.
Generally, in forming organic photosensitive layers, an organic photosensitive material is dissolved or dispersed in a solution of a resin in a solvent, and the obtained solution or dispersion is applied to a conductive substrate and dried. During this drying step, the solvent is removed from the organic photosensitive layer to form pores therein, and hence, the organic photosensitive layer has a somewhat porous structure. In addition, the solvent contained in the organic photosenstive layer is further reduced during the above mentioned storing period which is fairly long, so that the pores in the organic photosensitive layer are considerably increased. If a photosensitive member is manufactured by forming an amorphous hydrocarbon layer on such a porous photosenstive layer, and employed in a copying machine, the residual potential on the photosenstive member is disadvantageously raised during its repeated workings.
The present invention is intended to overcome the above discussed problems, and to improve the conventional photosensitive member comprising a surface protective layer of amorphous hydrocarbon formed on an organic photosensitive layer.